Interferon-beta 2/interleukin 6 is a co-stimulant for human T lymphocytes.

IFN-beta 2/IL-6 promotes the proliferation of human peripheral blood T cells in the presence of either PHA or Con A. This effect is observed with highly purified T cells and is masked by the addition of as few as 2% monocytes, suggesting that accessory cells are not required and that IFN-beta 2/IL-6 acts directly on the T cells. Both T4-positive and T8-positive cells respond to IFN-beta 2/IL-6 plus PHA. Studies of the time requirements of IFN-beta 2/IL-6 and of PHA in the response of T cells show that optimal co-stimulation occurs when both IFN-beta 2/IL-6 and PHA are added together at the outset of culture, suggesting that IFN-beta 2/IL-6 acts predominantly on resting T cells. Unlike T cell proliferation induced by IL-2, T cell proliferation induced by IFN-beta 2/IL-6 is not blocked by antibodies to the IL-2 R, suggesting that IFN-beta 2/IL-6 does not act by stimulating IL-2 production. Thus, in addition to its previously reported properties, IFN-beta 2/IL-6 stimulates T cells in the presence of mitogen, and may prove to be of considerable importance in the physiologic activation of T cells.